The invention relates to valve arrangements or valve assemblies and, in particular, relates to valve assemblies for transportable containers of the type serving to store and distribute a liquid under pressure from a propellant gas. The liquid to be stored and dispensed could comprise a beverage, a concentrate, a plant protection agent, or virtually any other transportable liquid.
The typical valve assembly of the above-mentioned type comprises (1) a ring-shaped stub secured in an upper opening of a container such as a barrel; (2) a valve housing; (3) a riser pipe arranged co-axially with an upper reception area in the valve housing such that the riser pipe and outlet valve can be displaced axially, against the biasing force of springs mounted within and about the valve housing, from an upper closed valve position to a lower open valve position; and (4) retaining parts which hold all parts in position within the stub. In previously-known valve assemblies of this type, the valve assembly can be readily disassembled before the gas pressure in the container has been fully relieved. Residual gas pressure in the container can force the valve components out of the container opening at high velocities with substantial risk to personnel and/or surroundings.
The problem of unauthorized disconnection of a pressurized container is addressed and at least partially solved in U.S. Pat. No. 5,242,092 to Riis et al. (the Riis patent). The valve assembly disclosed in the Riis patent includes, in addition to the stub, the riser pipe, valves, and springs, an obliquely and downwardly protruding finger provided on the lower free end of the riser pipe. The finger is spaced from the top of the riser pipe and cooperates with the remainder of the riser pipe such that the valve can only be dismounted completely when the riser pipe is in or in the vicinity of its bottommost position. Since pressure within the container forces the riser pipe upwardly and the finger therefore can be pushed into its lower position only in the absence of significant pressure, within the container, the finger functions to prevent damage which might occur if unauthorized persons were to attempt to disconnect the valve before the gas pressure in the container has been completely relieved.
The valve assembly disclosed in the Riis patent, though solving at least one of the problems exhibited by most valve assemblies, does not solve other problems associated with conventional valve assemblies. For instance, it cannot relieve excessive gas pressures within the container which may be generated when the container is subjected to external forces such as excessive shaking or other mechanical agitation or fire or other thermal agitation. The valve assembly disclosed in the Riis patent and other, traditional valve assemblies are designed only to keep the contents within the container, not to regulate the pressure within the container. Hence, traditional valve assemblies cannot prevent gas pressures within the container from reaching or even exceeding explosive levels in the presence of external agitation forces. Even if these external forces are less severe such that gas pressures within the container do not reach explosive levels, the higher-than desired pressure within the container still may render the contents dangerous to handle when making connection to dispensing equipment.
Another problem associated with previously-known valve assemblies is the problem of unintended and premature liquid escape during valve coupling. Presently-available valve assemblies are designed to cooperate with a coupling head which can be fixed in the valve or on the stub to form a sealed coupling. The coupling head, such as that manufactured by Perlick under the model number MK-1, connects the valve with a source of pressurized gas and with a liquid dispenser such as tapper. When the coupling head is seated and activated, an axially displaceable spindle is forced downwardly, setting-in-motion a two stage valve opening sequence. First the spindle comes in contact with the liquid valve plug, forcing it downwardly against a spring within the riser pipe, thereby opening the liquid passage. The spindle continues downwardly while making contact with the riser pipe itself, forcing the riser pipe downwardly against a second spring so that the riser pipe moves downwardly opening the gas passage, thereby completing the sequence and theoretically dispensing liquid only after the coupling head has been sealed and gas pressure has been applied. However, due at least in part to the fact that there are two separate pathways in the present assemblies, one being for gas and one for liquid, the liquid contents of the container is pushed to the very exit point of the liquid pathway by pre-existing gas pressure within the container. Now, when a per-activated coupling head is pressed into the I.D. of the housing, it will enter the liquid pathway before the coupling head seals against the container, thereby allowing the liquid contents to escape from the valve assembly and into the ambient atmosphere during the interval of time between initial liquid pathway opening and the time that the coupling head seals against the container.
Another disadvantage of the valve arrangement disclosed in the Riis patent lies in the configuration of its safety mechanism for preventing the valve from being removed completely from the container before the gas pressure in the container has been fully vented. That safety mechanism includes a relatively complex structure including an outwardly projecting finger on the valve cup or housing and a catch on a downwardly extending protrusion on the stub. An upper edge of the catch protrudes far enough from the wall of the housing to abut the inner side of the stub in all positions of the riser pipe when the catch is in a first position thereof, thereby preventing valve removal. When the catch is deflected to a release position, the outer end of the catch is substantially flush with the inner surface of the stub permit valve removal. This configuration is expensive to manufacture because it requires the provision of a special stub that extends below the surface of the container. Its catch is also difficult to fabricate and difficult to operate.